A wellhead stack assembly can be mounted below a rig floor. A wellhead stack assembly includes pressure control devices, including but not limited to devices such as a rotating control device (RCD) and one or more blowout preventers, for sealing wellbore pressure from atmospheric pressure. Controlling and containing downhole pressures protects workers and equipment on the rig floor from wellbore pressure during a drilling operation. These devices can include seal elements that can wear from contact with a drill pipe and fluid from the wellbore.